Electric winding



Feb. 17, 1948. w, J. BILODEAU ELECTRIC WINDING Filed Oct. 12, 1945 3Sheet S-Sheet l J .n V

Feb- 17, 1948- w. J. BILODEAU ELECTRIC .WINDING Filed Oct. l2, 1945 3Sheets-Sheet 2 Inventor: Wilfred lBlodeau, Ds His Attrrweg.

Feb. 17, 1948. w. J. BxLoDEAU ELECTRIC WINDING Filed Oct. 12, 1945 3Sheets-Sheet 5 a e me n od. r to o .H ,.C nB t f? w Patented Feb. 17,1948 ELECTRIC WINDING Wilfred J. Bilodeau, Windsor, Mus., assigner toGeneral Electric Company, a corporation of New York Application October12, 1945, Sorlal No. 621,915

8 Claims. (Cl. ITS-332) This invention relates to electric windings andmore particularly to improvements in the primary winding of a highvoltage current transformer. Y y

The primary'winding of-a current transformer for a high voltagealternating-current circuit is connected in series with oneof thecircuit conductors and it has insulation which is at least sumcient towithstand the voltage to ground of the conductor.l The voltagedifference between the terminals of the winding is, however, very smalland. therefore. the usual practice is to locate the primary winding asubstantial distance from its terminals andto connect the winding to itsterminals through leads which are close together and run parallel toeachother. The leads can be close together because they have a smallvoltage difference. whilethey are made long so that there can besufiicient insulation between the terminals and the casing or supportfor the primary winding and the rest of the transformer including itscore and secondary winding.

It is standard practice to surround the leads and also the primarywinding with a conductive shield which is inside the main insulation andwhich serves to grade or properly distribute the voltage stress in theinsulation. In ordinary primary windings for high voltage transformersthere is a substantial spacing between the start and finish of thewinding so that it is necessary to bend the leads across the winding soas to bring vthem together and inside of the electrostatic shield. Inthe larger size transformers the conductor is made of a heavy bar, orbars, of copper so that the conductor cannot be bent at a very sharplangle or on a small radius of curvature with the result that theconstruction becomes bulky and awkward at the start and finish of thewinding.

In accordance with this invention there is provided a novel windingwhich is characterized by transpositions of the strands forming theconductor of the winding in such a way'that the start and finish of thewinding come together at the same place and with minimu separation, thusreducing the size ofthe electrostatic shield and also minimizing sharpendsor corners which, as is well known. are points of high voltagestress.

An object of the `invention is to provide a new and improved electricwinding. "i

Another object of the inventi is to'provide an improved primary windingconstruction for high voltage current transformers.

A further object of the invention is to provide an improved electricinduction apparatus.

of a porcelain-clad instrument current transformer provided with anembodiment of the invention, Fig. 2 is an enlarged sectional view of Athe primary winding of the transformer shown in Fig. 1, Fig. 3 isanother sectional view of the same winding taken on line 3 3 of Fig. 2.Fig. 4 is an exploded perspective view of one of the two -coils of thewinding shown in Figs. aand 3. Fig. 5

is a development" of the conductor which forms the coil shown in Fig. 4with the strand insulation omitted. Fig. 8 is a perspective view of thecoil which is shown exploded in Fig. 4, Fig. rl is a cross sectionalview of the coil taken on line 1-1 of Fig. 6, Fig. 8 is a perspectiveview of a modification, Fig. 9 is an exploded view of the modificationshown in Fig. 8, and Fig. 10 is a development of the conductor whichforms the coil shown in Figs. 8 and 9.

Referring now to the drawing and more particularly to Fig. 1, thetransformer is shown as comprising a base tank I on which is mounted anelongated porcelain insulator 2 at the top of which are shown a pair ofhigh voltage terminals 3. Inside the tank and insulator is thetransformer proper comprising a core I, a low voltage coil l and a highvoltage coil 8. The low voltage coil is provided with leads 'l ending interminals i in a low voltage terminal box l. The high volt-M" agewinding is provided with leads Iii which are encased in a metal sheathii which also encases the high voltage coil. Surrounding this sheath issolid insulation i2 of any suitable type.

The high voltage primary winding B is shown in enlarged transversesection in Fig. 2 and it will be seen that it is symmetrical on bothsides of a vertical line through the middle. This is because it is madeup of duplicate two-tum coils il and i l. It will be observed that thecoils are located facing each other, so to speak, so that the leads ofthe two coils are at the center of the winding whereby there will beminimum spacing between the leads adjacent the winding. Each coil hastwo turns of a stranded conductor IB which has two side-by-side locatedgroups. each of four radially disposed strands. The coil i3 of Fig. 2

. is shown in Fig. 3, which is a section taken on line l-S of Fig. 2 inwhich the four radially disposed strands of the two laterally disposedgroups of conductors are clearly shown. It will also be seen from Fig. 3that the coil has two full turns and that its start and finish cometogether, and from Figs. 2 and 3 taken together it will be noted thatthe start and finish are also in the same 'I'he invention will be betterunderstood from radial plane of the coil so that there is minimum axial,as well as circumferential. spacing between them.

The way the strands of the conductor are transposed so as to form thecompact two-turn coil i3 is shown by the exploded perspective view inFig. 4, the development of its conductor in Fig. 5

i place at diil'erent asso, iss

and the compacted perspective view in Fig. 6. In these three gures thestart and ilnish ends of the coil or conductor, as the case may be. havebeen correspondingly labeled. Considering iirst, for example, a strandnumbered I6 which is visible in all three of the last mentioned ilguresand tracing it from start to iinish, it will be seen that afterapproximately one-eighth of a turn it is transposed laterally to theleft bythe width of the conductor I5, in which lateral position it re`mains until slightly more than one turn has been made. at which ally butthis time to the right or in the opposite direction and it thencontinues straight on in this latter position to the iinish where it hasthe same position relative to the other strands that it had at thestart. It will also be noted that between the two lateral transpositionsthe strand I8 is also transposed'radially from the top or outside to thebottom or inside and then after the second lateral transposition it isretransposed radially so that it finishes with the same radial positionthat it had at the start.

The position of the conductor i8 in Fig. 6 is indicated on Fig. 7 whichis a section taken on line 1--1 of Fig. 6. All oi' the other strandshave corresponding transpositions although they take circumferentiallocations on the coil. Furthermore, it will be noted that at one turnfrom the start and ilnish, that is to say. at the middle oi' the lengthof the conductor forming the two-turn coil, all oi the strands have beentransposed laterally the width of the conductor so that in effect theentire conductor has been transposed laterally. It is this which makesit possible for the start and finish to be at the same place in thecoil.

It is not essential that the conductor consist oi' laterally displacedgroups oi' parallel strands or that it have two turns and in themodication shown in Figs. 8, 9 and 10 the conductor consists of but onegroup of i'our radially superposed stands. In this modification theconductor continues from the start for three-quarters of a turn, beingfour strands high and one strand wide. The inner two strands are thenlaterally transposed and radially reversed so that i'or the next halfturn the conductor is two strands high and two strands wide. The outertwo strands are then similarly transposed to the left and radiallyreversed and the conductor then continues for one turn of one strandwide and four strands high and the strands.

have all been transposed the width of one strand to the left. At thispoint the inner strands are the right and reversed radially nextV halfturn the conductor is two strands high and two strands wide and atone-quarter oi.' a turn from the ilnish the outer strands areretransposed to the right and reversed radially so that all the strandsiinish in the same relative positions in which they start. Fig. A9 showsthe developed conductor oi' Fig. 10. which has just been described,coiled in three turns but the turns are separated so as to show how theturns nt together. The compacted threeturn coil shown in Fig. 8 will beseen to have an average thickness of six strands and to be two strandswide and it will be observed that, as in the previous modication, thestart and nish are as close as possible to each other, bothcircumferentially and axially. Obviously, also, two of the coils shownin Fig. 8 can be mounted face to face as are the coils I3 and I4 in Fig.2 so as to provide a six-turn two-coil winding. An advanpoint it isagain transposed latertage oi' the twocoil four-lead winding is that fselective series parallel connections oi the coils can be made so as toadapt the winding for use with circuits having a wide range oi current.

It will be observed from Figs. 6 and 8 that the coils are very cfipactand that the oblong cross section strands have not been twisted into nonparallel planes at any point in the coil and that the top and bottomsurfaces of all the strands remain essentially parallel with each otherat all cross sections of the coil so that there are aub= stantially nowaste spaces in the coil which are not illed with copper, except, oi'course, for the insulating wrapping aroundthe strands which is shown inFig. 4.

While there have been shown and described particular embodiments of thisinvention. it will be obvious'to those skilled in the art that variouschanges and modifications can be made therein without departing from theinvention and, there fore, it is aimed in the appended claims to coverall such changes and modifications as fall within the true spirit andscope of the invention.

What I claim as new and desire to secure Letters Patent of the UnitedStates is:

1. A multi-turn electrical coil for series connection in a line toground-said coil having at least one conductor with at least twostrands, said strands being radilfa ally superposed in the conductor atthe start and nish of said coil, said strands being axially and radiallytransposed an even number of times, said transpositions beingsuccessively reversed and be= ing so located circumferentially that thestart and finish of said coil have substantially the saine axial andradial position, linearly extending leads said coil and surrounding saidleads.

2. A circular multi-turn coil as dened in claim 1 in which the conductorcomprises two side-by side groups each oi at least two radiallysuperposed strands.

3. In a current transformer for high voltage circuits, a pair of highvoltage terminals, a c e cular whole numbered turn insulated primaryclosely adjacent parallel leads one of said leads, said winding havingat least one conductor consisting oi at least two strands, saidREFERENCES @FEED The following references are of record in the ille ofthis paten UNTED STATES PATENTS Germany having a high voltage relative

